Description

Thyroid eye disease (TED), also known as Graves' orbitopathy (GO), is the most common extrathyroidal manifestation of Graves' disease (GD). Its clinical course is heterogeneous, and it remains difficult to predict, at the time of GD diagnosis, which individuals will develop clinically significant eye involvement. Established risk factors, including smoking and elevated levels of TSH receptor antibodies, do not fully explain individual disease progression. Improved early risk stratification is therefore needed to identify participants who may benefit from closer ophthalmological monitoring and timely referral.

The SOGO study is a prospective observational cohort study conducted in the Capital Region of Denmark. It is designed to include a consecutive cohort of participants with newly diagnosed GD who reside in or receive clinical care within the Capital Region of Denmark. The region has approximately 1.9 million inhabitants, corresponding to approximately one-third of the Danish population. Based on Danish epidemiological data, the annual incidence of GD is estimated at approximately 30.7 cases per 100,000 inhabitants, corresponding to approximately 580 newly diagnosed cases annually in the region.

The study aims to enrol approximately 350 participants with newly diagnosed GD during the inclusion period from September 1, 2026, to August 31, 2028. Based on the expected number of incident GD cases during the two-year recruitment period, this target is considered feasible. The incidence of TED within the first year after a diagnosis of GD has been reported to be approximately 20% to 30%. The planned cohort size is expected to support exploratory analyses of associations between baseline clinical characteristics, ophthalmological findings, selected biomarkers, ocular surface microbiome characteristics, and the subsequent development of TED.

The study also includes two comparison groups, each comprising approximately 40 participants. The first is an age- and sex-matched healthy control group. The second comparison group will comprise participants with moderate-to-severe TED. both groups will provide comparative data on ophthalmological findings, biomarker profiles, and ocular surface microbiome characteristics.

The study is observational and does not involve randomization, experimental treatment, or changes to standard clinical management. However, participants will undergo study-specific research procedures, including standardized ophthalmological assessments, questionnaires, blood sampling, tear-fluid collection, and conjunctival ocular surface swab sampling. Some of these procedures may also be used in routine clinical practice when indicated, but they will be performed in this study according to a standardized research protocol. Diagnosis, treatment, and clinical follow-up of GD and TED will remain the responsibility of each participant's usual treating department.

Participants with newly diagnosed GD will be followed from baseline to approximately 12 months. Healthy control participants and participants with moderate-to-severe TED will attend one study visit. Study-related assessments will comprise the collection of structured clinical information, patient-reported outcome measures, standardized ophthalmological examinations, and biological samples.

The clinical assessment will include information on the onset and duration of symptoms, thyroid disease history, smoking status, relevant comorbidities, treatment history, and ocular symptoms. Patient-reported outcome measures (PROMs) will be used to assess ocular symptoms, thyroid-related symptoms, and health-related quality of life.

The standardized ophthalmological assessment will include visual acuity testing using a Snellen chart, colour vision testing using Ishihara plates, ocular motility assessment, assessment of diplopia, proptosis, optical coherence tomography (OCT), slit-lamp examination, fundoscopy, clinical photography of the eyes and periocular region, Schirmer testing, tear break-up time assessment, and conjunctival ocular surface swab sampling. These examinations will provide standardized research data on ocular surface status, orbital involvement, visual function, and early signs of TED.

Biological samples will include blood, tear fluid, and conjunctival swab samples from the ocular surface. Blood samples will be used for thyroid-related laboratory measurements and biomarker analyses, including analyses of inflammatory, metabolic, and proteomic markers. Tear fluid will be collected using Schirmer strips and analysed for biomarkers reflecting the ocular surface microenvironment. Conjunctival swab samples will be used to characterize the ocular surface microbiome, including microbial composition and diversity. The microbiome analyses are intended solely to characterize microbial material at the ocular surface. No analyses of participants' human DNA or hereditary genetic conditions will be performed.

Study data will be collected and managed using REDCap. Access to directly identifiable information will be restricted to authorized study personnel. Data will be pseudonymized before analysis, and direct identifiers will be stored and managed separately from the research datasets. Data quality will be supported by standardized data collection procedures, predefined variables, range and consistency checks where appropriate, and systematic review of key variables before statistical analysis.

Statistical analyses will be performed using standard statistical software. Descriptive statistics will be used to summarize baseline characteristics. Continuous variables will be presented as medians with interquartile ranges, while categorical variables will be presented as numbers and percentages. Between-group comparisons will be conducted using appropriate statistical methods. These may include the Mann-Whitney U test for continuous variables and the chi-square test or Fisher's exact test for categorical variables, as appropriate.

Associations between baseline clinical characteristics, biomarkers, microbiome characteristics, and incident TED will be evaluated using regression-based methods. Multivariable logistic regression will be used to evaluate TED status at approximately 12 months. Time-to-event analyses using Cox proportional hazards models may be conducted if the timing and number of events allow this approach. Analyses will account for relevant clinical covariates, including age, sex, smoking status, body mass index, thyroid biochemistry, and serum TRAb levels.

Receiver operating characteristic analyses may be used to evaluate the discriminatory performance of individual biomarkers or multivariable models. Exploratory biomarker and microbiome analyses will include appropriate measures of microbial diversity, composition, and relative abundance. Statistical planning, modelling, and interpretation of the biomarker and microbiome analyses will be conducted in collaboration with an experienced biostatistician.

The overall aim of the SOGO study is to generate clinically relevant knowledge that may support the earlier identification of people with newly diagnosed GD who are at increased risk of developing TED. In the longer term, the study may contribute to the development of clinically applicable risk prediction models and more individualized follow-up strategies for people with GD.